Many of you may have come across the issue of having a flickering video and for someone that's starting out in making videos it's not immediately apparent what the problem is or how to fix it.
The problem: The flickering problem is caused by shooting at a shutter speed lower or higher than the artificial light's frequency or 'hertz'.
What is HERTZ? Hertz is a measurement of frequency (how many times something happens during a given time) so in simple terms just means 'times per second'. In artificial light this means how many times the light turns on and off every second. Your power outlet is giving electricity out in 'waves' turning on and off 50 or 60 times every second. Any light you have connected to this will flicker 50 or 60 times every second. To the naked eye the light looks like it's just on, but a video camera can have problems with this waving light.
What is SHUTTER SPEED?
Shutter speed means how fast each picture is taken. The shutter is like a blind that opens and closes to let light in. When shooting video an image is taken 30 times every second (Most cameras shoot at 24, 25, 30, 50 or 60 frames per second, depending on your camera and settings.) Shutter speed means how long the camera opens the shutter for each individual frame. (Note: On digital cameras there is no actual opening shutter mechanism, it's all digital.) Shutter speed is measured in parts of a second. For example, 1/50s means one fiftieth of a second. Take one second, split it into 50 parts, take one of those parts and you have 1/50s.
Here is an example:
How to fix the problem: There are a few things you could do: The first is to set a correct shutter speed. Shooting at 1/50s or 1/60s depending on your country (If you are not sure what the frequency is in your country just check this list). Many times you will get away with using lower or higher shutter speeds, sometimes exactly double the hertz of the light (using 1/100s in a country which has a 50 hertz power output) will be okay - but ALWAYS double check if it's an important shoot. Flicker is not always visible on the camera's LCD screen. You may have to offload the footage onto a computer in order to make sure you're not getting any flicker. In my experience you can see it on most cameras as long as you're looking for it. Note: Using a shutter speed above 1/60s can look choppy. The higher the shutter Your other option is to use a light that does not flicker..
What lights flicker and what lights don't? Any light that runs on DC power should be flicker free if it does not have anything else (like a dimmer) causing flickering. DC means Direct Current. It means that the power is stable rather than flickering on and off like AC (Alternating Current). You know those big bricks that come with some household devices? Printers, cameras, etc. Well those are (usually) DC adapters (Sometimes it's a beefy plug rather than an in-line 'brick'). They convert the alternating current coming from the power outlet into direct current which is a non flickering beam of light. Any light that uses a DC adapter or runs on batteries should be completely flicker free, although many manufacturers use dimmers in LED lights that can also cause flickering because they turn the light on and off very fast to reduce the light output, but this kind usually can't be fixed by changing the shutter speed like you can do for AC lighting. An LED light that does this should be returned to the seller. The sun's rays do not cause any flicker on video cameras, so use some sunlight if it suits your shoot.